Ken Follett established himself in the thriller genre with this novel, first published in 1978. It was an instant bestseller and later made into a movie with Donald Sutherland and Kate Nelligan.
The premise: Henry Faber (codename: "Die Nadel") an individualistic and ruthless German agent (one of the last German spies not scooped up by MI5) is assigned to investigate whether or not Lt. General Patton's First United States Army Group is massing in East Anglia for the expected invasion of Calais, the area the German High Command expects the Allies to assault. Faber discovers that Patton's Army is a phony. The Allies are deceiving German intelligence with fake messages, troop concentrations and dummy barracks (which look real to German reconnaisance aircraft).
However careful as Faber is, the British counterintelligence agents Percival Godliman and Fred Bloggs, a history professor and policeman respectively, are a brilliant team that discover "Die Nadel" and are hot on his trail.
Eluding the police and the Home Guard and killing any and all who suspect his identity, Faber heads north to make a rendezvouz with a U-boat. His escape is thwarted by bad weather and he is washed ashore on Storm Island, a nearly deserted piece of rock in the North Sea, where Lucy Rose, a beautiful, but frustrated wife of a legless RAF pilot lives. In time, she discovers Faber's true identity....
I don't usually like thrillers, but this one kept me up. I read it over 20 years ago and have read it a few times since. Follett is a good story teller and his research for the story is wonderful. His portrayals of the German leaders, Hitler, Rundstedt and Rommel are superb.
I liked the film version too, though I believe it would be ideal for a remake (my choices for Faber would be Ralph Fiennes and for Lucy Kate Winslett or Helena Bonham Carter).
Time hasn't dimmed this book. It still holds up and is a classic of World War II espionage. Enjoy.